Where a stream is to pass under a roadway, there are generally two alternatives which may be employed to permit the stream to pass under the roadway. The first is the construction of a bridge which spans the stream. This can be extremely expensive, especially in applications where the culvert to be crossed is relatively narrow. The other alternative is the use of concrete culvert systems. These systems typically utilize precast concrete culvert sections which are placed adjacent one another until they extend essentially the width of the road to pass over the culvert. At the opposing ends of the aligned sections are placed respective pairs of concrete wingwalls which can assist with the controlling of water flow beneath the culvert and to prevent the erosion of the ground near the ends of the aligned culvert sections. On each side of the culvert is a concrete footer on which the aligned culvert sections and wingwalls rest.
Typically the wingwalls associated with the prior art have not been precast. Instead a contractor pours cast-in-place wingwalls following the alignment of the precast culvert sections. To retain the wingwall atop a footer, a series of steel reinforcing rods extend upwardly into the upright portion of a wingwall, which portion is known as the "stem", about 3'. However, utilizing cast-in-place wingwalls typically consumes one to two weeks of additional construction time, with this time associated with the pouring and curing of the four wingwalls.
Additionally, since it is necessary to exhibit control over the curing process, problems can arise concerning the quality control associated with the wingwalls in the event there are any problems with the culvert system over time. Further, weather can present a problem where the wingwalls are cast-in-place, especially in parts of the country which experience extremely low temperatures.
Because of concerns over quality control, a precast wingwall has recently become available and is disclosed in U.S. Pat. No. 4,993,872. The wingwall associated with that patent is physically attached to the end-most culvert sections at opposite ends of the culvert system. Additionally, in an attempt to limit movement of that wingwall, a thrust block is utilized. Both the physical attachment of the wingwall to the culvert section the utilization of a thrust block highlight the extreme desirability of preventing the wingwall from moving from its original placed position.
However, a problem with precast concrete wingwalls which are physically secured to an end-most culvert section is that any settling problems associated with the footer near the wingwall can impart substantial forces on the retention means securing the wingwall to the end-most culvert section. These forces may precipitate the failure of the culvert section-wingwall attachment, resulting in settlement of the wingwall. This instability of the wingwall can result in undesirable movement, perhaps in total collapse of the wingwall, thereby necessitating significant repair to the culvert assembly. Therefore, it would be desirable to utilize a precast concrete wingwall not suffering from any of the disadvantages associated with the prior art.